There is a prior art method of sealing bottles by means of plain caps which, when they are applied to the threaded necks of bottles to seal them, are deformed by rolling so that they match the shape of the threaded neck. Essentially, the rolling operation enables the profile of the threads of the threaded necks of bottles to be copied, or more correctly to be formed, in the caps.
In general, each cap has an end ring of specified height, which is connected by breakable links to the skirt of the threaded cap. The function of the end ring is to form a security seal which can demonstrate the integrity of the seal formed by the cap.
For this purpose, during the rolling operation the end ring is pressed and deformed against an edge of the threaded neck which forms a stop to prevent the axial movement of the end ring. Consequently, the unscrewing of the threaded cap from the neck of the bottle causes the links to break, thus making the opening of the bottle evident.
The prior art includes single capping machines, in other words those which can operate on one bottle at a time, and multiple machines, in other words those which can operate on more than one bottle at a time.
Some machines of the second type receive the bottles, with the caps already placed on their necks, from a conveyor belt; the bottles are picked up from the belt and placed on a rotating support, which carries them along a circular path so that they revolve around the principal axis of the machine.
During this circular movement, the capping machine operates the screwing/rolling heads in a known way, so that, during the revolution around the principal axis of the machine, one head is present above each bottle. The heads are also made to rotate about their own axes; in other words, they rotate with respect to the bottles.
During its rotation around the machine, each head is first brought towards the bottle, to carry out the thread copying and rolling required to create the seal; the head is then moved away from the bottle, leaving the latter free to continue in the production cycle.
Earlier machines, designed to have high output rates, have operating parameters which are not modifiable and which have been optimized specifically for capping operations using plain, unthreaded caps.
Recently, new caps have been introduced, reproducing externally the appearance of conventional bottles with corks; however, these caps are threaded internally so as to be adapted to the bottles with threaded necks present on the market.
The capping machines for applying these new caps must therefore be capable of screwing the cap fully on to the bottle before starting the operation of rolling the seal on the security collar.
A head capable of carrying out these operations is described in the patent WO 2004/005181, in the name of Pechiney. However, this head has the drawback of not being usable on the multiple capping machines developed for use with copying and rolling heads, since it is specific to newly designed machines and requires operating parameters which are completely different from those for which the existing machines were designed.
In the first place, it is necessary to consider that the operation of existing capping machines can be described in terms of four operating phases:                a first phase in which the copying and rolling head, rotating with respect to the bottle, approaches the cap with a downward rotary-translational movement; this phase is optimized to be as fast as possible;        a second phase, in which the head copies the thread and forms the security seal; in this phase, the head is rotating with respect to the bottle but does not make any axial movement with respect to it;        a third phase, symmetrical to the first one, in which the head moves away from the bottle;        a fourth phase, in which the capped bottle completes its cycle and is transferred to the output belt to allow another bottle to take its place on the rotating support; in this phase, the head does not make any axial movement.        
In view of the state of the art described above, the object of the present invention is to provide a screwing/rolling head which has structural and functional characteristics such that it can also be applied to capping machines of the old type with non-modifiable operating parameters, and which enables these machines of the old type to be used for applying the new types of plain threaded caps to standard threaded containers or bottles.